For Ultra-Cold Neutrino Experiment, a Successful Demonstration 9 April 2015, by Kate Greene

For ultra-cold neutrino experiment, a successful demonstration 9 April 2015, by Kate Greene

Second, the experiment, successfully demonstrates the performance of CUORE's novel design—a detector made of towers of Rubik's cube-sized crystals of tellurium dioxide. These towers are placed in a high-tech refrigerator that has been painstakingly decontaminated, shielded from cosmic rays, and cooled to near absolute zero.

Today's results represent data collected over two years from just one tower of tellurium dioxide crystals. By the end of the year, all 19 towers, each containing 52 crystals, will be online, increasing CUORE's sensitivity by a factor of 20.

Assembly of the CUORE-0 detector array in a cleanroom "CUORE-0 is so far the largest detector operating at Gran Sasso National Laboratory. Credit: CUORE collaboration at a temperature very close to absolute zero," says Dr. Oliviero Cremonesi of INFN-Milano Bicocca, spokesperson for the CUORE collaboration. "CUORE is presently in its final stages of Today an international team of nuclear physicists construction, and when completed, it will study the announced the first scientific results from the nuclear processes associated with the Majorana Cryogenic Underground Observatory for Rare neutrino with unprecedented sensitivity." Events (CUORE) experiment. CUORE, located at the INFN Gran Sasso National Laboratories in "With the CUORE-0 results, we've proven that our Italy, is designed to confirm the existence of the experimental design, materials, and processes, Majorana neutrino, which scientists believe could which include extremely clean surfaces, pure hold the key to why there is an abundance of materials, and precision assembly, are paying off," matter over antimatter. Or put another way: why says Yury Kolomensky, senior faculty scientist in we exist in this universe. the Physics Division at Berkeley Lab, professor of physics at UC Berkeley, and U.S. spokesperson for The results of the experiment, called CUORE-0, the CUORE collaboration. were announced at INFN Gran Sasso Laboratories (LNGS) in Italy, the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab), and at other institutions in the US.

The findings are twofold. First, the CUORE-0 results place some of the most sensitive constraints on the mass of the elusive Majorana neutrino to date. With these new constraints, the CUORE team is essentially shrinking the size of the haystack that hides the Majorana needle, making it much more likely to be found.

1 / 3

neutrinoless double-beta decay would lead us directly to the Majorana particle, and give us hints as to why the universe has so much more matter than antimatter."

Known laws of physics forbid such matter- antimatter transformations for normal electrically charged particles like electrons and protons. But neutrinos, which are electrically neutral, may be a special kind of matter with special capabilities.

The proposed matter-antimatter transitions, while extraordinarily rare now, if they happen at all, may have been common in the universe just after the big bang. The remainder of existence, then, after all the annihilations, would be the matter-full universe we see today.

Crystal Clarity

The CUORE crystals of tellurium dioxide are View of the detector before insertion into the cryostat. packed with more than 50 septillion nuclei of Credit: CUORE collaboration tellurium-130, a naturally occurring isotope that can produce double-beta decay and possibly neutrinoless double-beta decay. For the experiment, the crystal towers sit in an extremely Annihilations in the Early Universe cold refrigerator called a cryostat that's cooled to about 10 milliKelvin or -273.14 degrees Celsius. To pin down the Majorana neutrino, the Last year, the CUORE cryostat set a record for researchers are looking for a telltale indicator, a being the coldest volume of its size. rare nuclear process called neutrinoless double- beta decay. This process is expected to occur In the very cold CUORE crystals, presence of both infrequently, if at all: less than once every septillion nuclear processes would produce small but (a trillion trillion, or, a 1 followed by 24 zeros) years precisely measured temperature rises, observable per nucleus. by highly sensitive temperature detectors within the cryostat. These temperature increases correspond Unlike regular double-beta decay, which emits two to spectra—essentially the amount of energy given anti-neutrinos, neutrinoless double-beta decay off—from the nuclear event. Two-neutrino double- emits no neutrinos at all. It's as if one of the anti- beta decay produces a broad spectrum. In contrast, neutrinos has transformed into a neutrino and neutrinoless double-beta decay would create a cancelled—or annihilated—its sibling inside the characteristic peak at the energy of 2528 nucleus. kiloelectron-volts. This peak is what the researchers are looking for. "In 1937, Ettore Majorana predicted that neutrinos and anti-neutrinos could be two manifestations of The CUORE experiment sits about a kilometer the same particle – in modern language, they are beneath the tallest mountain of the Apennine range called Majorana particles," says Reina Maruyama, in Italy, where rock shields it from cosmic rays. This assistant professor of physics at Yale University, location, as well as the experimental design, and a member of the CUORE Physics Board, which enables the sensitivity required to detect guided the analysis of the data. "Detecting neutrinoless double-beta decay.

2 / 3

"The sensitivity demonstrated by the results today is outstanding," says Stefano Ragazzi, director of the INFN Gran Sasso National Laboratories. "The INFN Gran Sasso Laboratories offers a worldwide unique environment to search for ultra-rare interactions of Majorana neutrinos and dark matter particles and is proud to host the most sensitive experiments in these fields of research."

"While there's no direct evidence of the Majorana neutrino yet, our team is optimistic that CUORE is well positioned to find it," says Ettore Fiorini, professor emeritus of physics at the University of Milano-Bicocca and founding spokesperson emeritus of the experiment. "There is a competition of sorts, with other experiments using complementary techniques to CUORE turning on at about the same time. The next few years will be tremendously exciting."

Provided by Lawrence Berkeley National Laboratory APA citation: For ultra-cold neutrino experiment, a successful demonstration (2015, April 9) retrieved 2 October 2021 from https://phys.org/news/2015-04-ultra-cold-neutrino-successful.html

This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.

3 / 3